Autonomous movement devices that autonomously move in accordance with an application are becoming popular. For example, autonomous movement devices that autonomously move for the purpose of indoor space cleaning are known. In general, as for such autonomous movement devices, creation of a map in an actual space and estimation of the local device position in the real space are necessary.
As for the scheme of creating a map in the actual space, for example, a Simultaneous Localization And Mapping (SLAM) scheme has been known. The basic principle of the SLAM technology using a monocular camera is disclosed in Non Patent Literature 1 and Non Patent Literature 2, and by tracking the same feature point from the multiple frames of a motion image picked up by the camera, a process of alternately estimating the three-dimensional position of the local device (camera position) and the three-dimensional position of the feature point (this is collected up to form map information) is executed.
According to this scheme, since the local device position and the three-dimensional position of the feature point are alternately estimated, an error accumulation occurs. Hence, even if a looped movement, or the like is performed to return to the original position, devices are sometimes unable to recognize the return to the original position. As for a scheme of correcting such an error accumulation, there is known a technology called a loop closing process (a loop resolution process) that is disclosed in Non Patent Literature 3. According to this loop closing process, when the local device detects a loop (when the local device detects that the picked-up frame is similar to the frame picked up in past), the local device estimates the position at that past time as a proper position, and corrects the positions on the route reaching the present position from the estimated proper position, thereby reducing the error.
Non Patent Literature 1 Andrew J. Davison, “Real-Time Simultaneous Localization and Mapping with a Single Camera”, Proceedings of the 9th IEEE International Conference on Computer Vision Volume 2, 2003, pp. 1403-1410
Non Patent Literature 2 Richard Hartley, Andrew Zisserman, “Multiple View Geometry in Computer Vision”, Second Edition, Cambridge. University Press, March 2004, chapter 9
Non Patent Literature 3 NARA INSTITUTE OF SCIENCE AND TECHNOLOGY, Information Science, Associate Professor SATO Tomokazu, “SSII2015 Tutorial, Sequential Three-dimensional Reproduction from Motion Image by Feature Point Tracking, and Application Thereof, from Basics of Coordinate System to Application Case Examples and Recent Research Tendency”, [online], Jun. 10, 2015, Image Sensing Symposium Tutorial Lecture Meeting, [searched on Feb. 22, 2016], Internet <URL: http://yokoya.naist.jp/paper/datas/1407/SSII%E3%83%81%E3%83%A5%E3%83%BC%E3%83%88%E3%83%AA %E3%82%A2%E3%83%AB%E4%BD%90%E8%97%A4.pdf>